Well drilling apparatus



Febl, 1966 R. H. CULLEN ETAL WELL DRILLING APPARATUS Filed Nov. l2, 1963 MECA@ f @HHM M .Jew MM/ Hma w @www #man Fel l 1966 R. H. cULLl-:N ETAL 3,232,362

WELL DRILLING APPARATUS Filed Nov. l2, 1963 3 Sheets-Sheet. 2

Fd@- l 1966 R. H. CULLEN ETAL 3,232,362

WELL DRILLING AIPARATUS United States Patent 01 3,232,362 WELL DRILLING APPARATUS Roy H. Cullen, Suite 1931, 500 Jefferson Bldg., Houston, Tex., and Charles H. Elliott, Jimmie R. Aker, and Thomas J. Gilchrist, Houston, Tex.; said Elliott, said Aker, and said Gilchrist, assignors to said Cullen Filed Nov. 12, 1963, Ser. No. 323,024 Claims. (Cl. 1752-404) This invention relates to new and useful improvements in well drilling apparatus.

Ordinarily, a well is drilled by imparting rotation to a drill bit through a tubular drill string. In some instances, drilling is effected today with exible drilling hose instead of the tubular pipe forming the normal drill string. When the iexible hose has been used, the bit has been rotated by a duid-driven engine, but so far as is known, all prior eiforts to rotate the bit wtih an electric motor have been unsatisfactory.

It is an object of the present invention to provide a new and improved well drilling apparatus wherein the drill bit isfrotated with an electric motor disposed in the well.

An important object of this invention is to provide a new and improved drilling apparatus having in combination a shock absorber and a slip clutch connecting a motor to a drill bit so that intermittent shock loads from the bit are decelerated by the shock absorber to reduce the torque change transmitted to the slip clutch, thereby reducing the amount of wear on the parts of the clutch and possible damage to the motor.

Another object of this invention is to provide a well drilling apparatus having a new and improved slip clutch which allows slippage in the drive connection between a motor and a drill bit when the torque acting thereon exceeds a predetermined amount, so that if the drill bit suddenly is caught in the formation being drilled and is thereby prevented from rotating, the clutch functions to prevent damage to the motor.

A further object of this invention is to provide a well drilling apparatus having a new and improved shock absorber which is adapted to transmit rotational power from a motor to a drill bit while absorbing intermittent shocks that may otherwise damage the motor.

Still another object of this invention is to provide a new and improved drilling apparatus having a slip clutch and Ya shock absorber connected between a motor and a drill bit, with at least the slip clutch operating in an oil bath, and with drilling fluid circulating around the motor, clutch and shock absorber to remove heat generated thereby in use.

An additional object of this invention is to provide a new and improved drilling l.apparatus wherein an electric motor or turbine is connected in driving relationship to a drill bit with a slip clutch, gear train and shock absorber, and wherein the gear train is protected against damage from shock loads and from .sudden stoppage of the bit rotation by such shock absorber and slip clutch.

A particular object of this invention is to provide a new and improved shock absorber which has a length greater than its diameter so that it is capable of transmitting large torques with a relatively small diameter apparatus without damaging the flexible elements of the shock absorber.

The preferred embodiment of this invention will be described hereinafter, together with other features thereof,

and additional objects will become evident from such description.

The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown, and wherein:

FIG. 1 is a View, partly in section and partly in elevation, schematically illustrating the well drilling apparatus of this invention;

FIG. 2 is a vertical sectional View, partly in elevation, illustrating the details of the slip clutch forming a part of the well drilling apparatus of FIG. l;

FIG. 3 is a cross-sectional view taken on line 3-3 of FIG. 2 to further illustrate the details of the slip clutch;

FIG. 4 is a vertical sectional view, partly in elevation, illustrating in detail the shock absorber forming a part of the well drilling apparatus of this invention;

FIG. 5 is a cross-sectional view taken on line 5-5 of.

FIG. 4 and illustrating further details thereof;

FIG. 6 is a view, partly in elevation and partly in section, schematically illustrating a moditied form .of the invention;

FIG. 7 is a cross-sectional view taken on line 77 of FIG. 6; and

FIG. 8 is a View, partly in section and partly in elevation, schematically illustrating a portion of another modiiication of the present invention.

In the drawings, the letter A designates generally the Well drilling apparatus of this invention which is adapted to be disposed in a hole for the drilling of an oil well or the like. As schematically illustrated in FIG. 1, the apparatus A includes a housing or drill collar 10 into which a motor M is press-fitted or otherwise secured for driving a drill bit B to drill the well. The motor M is interconnected with the drill bit for imparting rotation thereto, and for accomplishing such drive, a slip clutch C and a shock absorber S are included in the connection between the motor and the bit. By reason of the present invention, the motor M is located in the well in proximity to the drill bit B and is protected against damage during drilling by the interaction of the shock absorberS and the slip clutch C, while at the same time drilling fluid is circulated to dissipate heat generated by the motor M and other apparatus, as will be more evident hereinafter.

In FIG. l of the drawings, a housing or drill collar 10 is schematically illustrated. The upper end of the housing 10 is connected to a drill string which preferably is4 a flexible hose type of drill string. For conducting elec trical power to the motor M, an electrical cable 12 extends from the surface of the well tothe motor M as seen in FIG. l. Such electrical cable thus extends inside of the flexible hose or other drill string so that the drilling mud or other drilling fluid which ows through the drill str-ing to the drill bit ilows around such cable 12. The cable 12 is of course insulated to prevent any short circuiting. In order to prevent the mud within the drill string from entering the area where the motor M and the clutch C are located, a seal or packing 14 is mounted in the housing 10 above the motor M for providing a duid-tight' seal around the cable 12. Such packing 14 is preferably carried by a disc or plate 16 having the packing as a central opening through which the cable 12 extends. An additional seal 20 is provided below the slip clutch C so that the area between the seal 14 and the packing or seal 20 is sealed oi from the drilling mud or fluid.

In vorder to convey the4 drilling mud or fluid around such sealed olf area and deliver it to the drill bit B for drilling purposes, an annular sleeve 22 or alternatively, longitudinal tubes, are welded or otherwise formed on the housing for bypassing uid from above the plate 16 to the area below the packing 20 through housing openings 11a and 11b.

Preferably the sealed olf area between the packing elements or assemblies 14 and 20 is lled with oil or other lubricant which further assists in preventing an intrusion of the drilling mud into the vicinity of the motor M and the slip clutch C. To allow for fluctuations in mud and oil pressures in the system, any suitable compensating means such as indicated by the flexible diaphragm 10a may be employed. A more detailed type of pressure compensating apparatus is illustrated in FIG. 6, which may be used in the FIG. l form of the invention if desired.

The drilling mud is discharged from the housing 10 into a bore 23a of a drill bit shank 23 through suitable lateral openings 23b. The drillingmud then flows through the drill bit B for discharge therefrom during the drilling operation in a conventional manner. Bearings such as indicated at 24 may be provided to facilitate the rotation of the drill bit B with respect to the housing 10 and the rest of the drill string connected thereabove.

The motor shaft 25 (FIGS. '1 and 2) is suitably connected to the upper end of a cylindrical shell 26 forming the outer shell of the slip clutch C. Preferably the connection between the outer shell 26 and the motor shaft 25 is with splines 25a which intert with corresponding splines in the boss 26a at the upper end of the sleeve 26. The inner surface or bore 2Gb is cylindrical and is ground and polished smooth, preferably being formed of a heat treated alloy steel; such bore 2Gb is open at the lower end as viewed in FIG. 2 for substantial radial exing, whereby such shell 26 is expansible.

A plug designed generally With the numeral 30 extends within such bore 26b for frictional engagement therewith. The plug 30 has a lower boss 30a which is internal- 1y splined for connecting to a drive shaft 31 having suitable splines 31a or other connecting means therewith.

The boss 30a is preferably cylindrical in construction and has a plurality of expansible plug elements or fingers 32 formed therewith (FIGS. 2 and 3). Each of such expansible elements 32 is adapted to move substantially radially outwardly into frictional engagement with the inner surface or bore 26h so as to lock the elements 32 and the shell 26 together for rotating the shafts 25 and 31 together, as will be more'fully explained.

The resilient or flexible elements 32 are preferably three in number as best seen in FIG. 3, although the number thereof may vary according to circumstances and the size of the entire assembly. In order to expand such elements 32 outwardly so as to engage the inner surface 26h with a predetermined frictional force, a wedge or expander 35 is disposed centrally with respect to such elements 32 and is provided with an external frusto-conical surface 35a which engages wit-h inner tapered surfaces 32a. Thus, as the expander 35 moves downwardly with respect to the elements 32, as viewed in FIG. 2, such elements 32 are expanded radially outwardly. On the other hand, as the expander 35 moves upwardly with respect to the elements 32, the inherent resiliency of the elements 32 returns them to an inward position to reduce the amount of frictional force, or even eliminate such frictional force between the elements 32 and the inner surface 26b. In order to prevent a galling between the contacting surfaces 32b of the expansible elements 32 and the inner cylindrical surface 26b of the shell 26, the shell and the elements 32 are made of materials which do not gall when in engagement with each other. For example, the external surface of the elements 32 may be made of a manganese bronze when the inner surface 2Gb is ground and polished smooth alloy steel.

It will be understood that other materials may be readily used so long as the materials are compatible and do not gall when in engagement and moving with respect to each other.

The expander 35 has an internal end opening with flat surfaces 35b for receiving an Allen wrench or a similar device in order to rotate the expander 35. The lower end of the expander 35 has an externally threaded projection 35e with threads 35d formed thereon for engagement with internal threads 30b so that upon a rotation of the expander 35, the position of the expander 35 with respect to the friction elements 32 may be adjusted for thereby 4adjusting the amount of the frictional engagement between the surfaces 32b and 26b. v

For assembly purposes, an annular groove 26e` is provided at the lower end of the outer shell 26 for receiving a snap ring 3S formed of metal or the like. Such snap ring is preferably in engagement with a spacer ring 40 disposed below a shoulder 30C of the plug 30.

Referring now to FIGS. 4 and 5, wherein the details of the preferred form of the shock absorber S are illustrated, it can be seen that the upper end of the shock absorber S is preferably connected to the shaft 31 or an extension thereof. The lower end of the shock absorber S is connected to another shaft 41 which may be (FIG. l).

The shock absorber S includes a hollow housing 42:

h-aving an open lower end 42a for providing an entrance to the bore 42b. A boss 42C is provided at the upper end for receiving the shaft 31. Preferably, the shaft 31 has external splines 31b formed thereon which intert with corresponding internal splines within the boss 42C. connecting means may be employed for connecting the shaft 31 to the housing 42. Openings 42d are provided at the upper end of the housing 42 for introducing mud or other drilling fluid into the -bore 42b for the purpose of cooling the internal portions of the shock absorber S in use, as will be more evident hereinafter. u

In the preferred form of the invention, the housmg 42 is formed with longitudinal slots 42e (FIG. 5), each of which is adapted to receive a vane 50 which extends longitudinally within the bore 42b. Each vane 50 is welded as indicated at 50a to secure same to the housing 42 so as to actually become an integral part of such housing 42. If preferred, the vanes 50 may be preformed as an integral part of the housing 42, but the construction illustrated is ordinarily more desirable because it facilitates manufacturing.

A paddle 55 is adapted to extend into the bore 42b of the housing 42. Such paddle 55 is preferably constructed with a central mandrel 55a which has integrally formed therewith, or secured thereto, a pair of paddle elements 56. The number of the paddle elements 56 may vary, but preferably the number of such paddle elements 56 corresponds with the number of the vanes 50. The man'- drel 55 is preferably formed integrally with a lower boss 55b which is adapted to be connected to the lower shaft 41 by the interconnection of splines 41a on the shaft 41 with internal splines within the boss 55b. Other suitable connecting means may of course be employed for making such connection between the shaft 41 and the boss 55b. r

For transmitting rotational movement from the housing 42 and the vanes 50 to the paddle 55 and thus'to the shaft 41, the shock absorber S includes a resilient deformable rod or element 60 between the adjacent surfacesof each of the vanes 50 and the paddle elements 56.: Thus; in the form of the invention illustrated inFIGS. 4 and 5, there are four of such resilient rods 60. Each of the resilient rods is formed of a deformable flexible material such as an elastomer of the Buna-N rubber type. -By way of example, such rod mayhave a durometer of eighty, although the invention isvnot limited thereto. The prefer- It will be apppreciated that other suitable El u able shape for such rods 60 is cylindrical as illustrated in the drawings, but the shape may vary so long as there is a suitable space between the rod and each of the vanes 50 and paddle elements 56 to permit a flexing and some distortion of the rods 60 in the transmission of the rotative movement of the shaft 31 to the shaft 41. By reason of the resiliency of the flexible elements or rods 60, shock loads which occur for a relatively short period of time in the drilling with the bit B are absorbed or reduced in intensity, thereby reducing the amount of shock transmitted to the clutch C and the motor M.

Since the rubber or other elastomer forming the rods 60 becomes heated during the absorption of shock loads, the drilling mud maintains such rods 60 cool by flowing through the openings 42d and discharging through the lower openings 62a. It is also important to note that the shock absorber is greater in length than in diameter, this being to provide an adequate torque distribution to the elastomer rods 60. The torques transmitted by the shock absorber S are relatively high particularly in view of the small diameter of the absorber S, but such loads are adequately handled with the absorber S because the rods 60 are relatively long so as to distribute the loads to a greater surface area thereof for preventing shearing or other disintegration of the rods 60.

For stabilizing the assembly, a stabilizing ring 62 having openings 62a therethrough is held below the rods 60 by a removable snap ring 65. The snap ring 65 is preferably mounted in an annular groove 42f in the lower open end 42a of the housing 42.

In the use or operation of the drilling apparatus of this invention, the apparatus A is preferably lowered into the well bore or hole on a iiexi'ble hose or similar type of drill string. With the drill bit B positioned on the bottom of the hole for drilling, the drilling mud or other fluid, liquid or gas, is circulated through the drill string and down through the bypass tubes or sleeves 22 to the drill bit B. The electrical power is supplied to the motor M through the electrical cable 12 which thereby drives the drill bit B in a rotational direction through the drive connection which includes the clutch C and the shock absorber S.

During the drilling, a large amount of heat is generated by the various parts of the apparatus, particularly the motor M, the slip clutch C and the shock absorber S. The circulating fluid which flows in the sleeve 22 around the oil bath dissipates the heat generated in the oil bath so as to continuously remove heat from the motor M and slip clutch C. Also, the mud or other iluid removes heat generated by the shock absorber S.

When the bit B hits a hard section or formation during drilling, and temporarily is slowed down, the shock of such initial slowing of the drill bit B in its rotation is initially absorbed to some extent, and possibly entirely, by the action of the shock absorber S. By reason of such initial shock absorbing with the shock absorber S, the slip clutch C is prevented from slipping frequently as would normally occur in the absence of the shock absorber S. Therefore, Wear on the friction elements 30 and the internal surface 32b of the slip clutch C is reduced by the presence of the shock absorber S in the apparatus.

In the event the drill bit B becomes stuck and cannot rotate further, the load imposed upon the motor M will disconnect the electrical power to the motor M by throwing a circuit breaker (not shown) of conventional construction at the surface of the Well. Thus, the electrical power to the motor is cut off so that the motor no longer is being driven by the electrical power. However, even when the motor is no longer being supplied with the electrical power, there is a momentum which remains within A fil damaging the electrical portions of the motor M itself. However, with the present invention, when the motor M is no longer supplied with the electrical power due to the circuit breaker cutting orf such power, the torque load then imposed upon the shaft 25 as it tries to continue to turn is suilicient to cause the shell 26 to rotate relative to the friction elements .32 and thereby cause a slipping or relative movement of such parts. The slipping of such clutch parts therefore relieves the torque load on the motor shaft 25, leven though the lower shaft 31 which is connected to the drill bit B indirectly, can no longer turn'due to the fact that the drill bit B is stuck.

IIn .some instances, the motor M may not become loaded suiicient-l-y to throw the circuit breaker and thereby out off the vcable 12, but a temporary load is placed upon the drill hit B by reason of an extremely hard formation or obstruction within the well bore. In such cases, t-he same action of the slip clutch C takes place, perrrutting a relieving of the torque load on the motor shaft 25 through the slipping of the outer shell 26 with lrespect to the friction lingers or elements 32.

In FIGS. 6 and 7, a modification of the invention is illustrated wherein the apparatus A-1 corresponds with the apparatus A of FIG. l, except that a gear train G and a pressure equalizin-g section E are incorporated in the apparatus A-l. The parts of the apparatus A-1 which are identical or similar to the apparatus A of FIG. 1 are indicated with the same letters or numerals.

The ygea-r train G is connected to the slip clutch C through a shaft 1311 which :corresponds with the shaft 31 of FIGS. 1 and 2. However, fthe shaft 131 is a pinion shaft which has a pinion gear 13111 formed at its lower end for Imeshing with a plurality of idler gears 70. The idler gears are adapted to engage the internal gear teeth of an internal ring gear 71 which is preferably formed integrally within the housing or tubular body 10.

'Ilhe idler gears are Asupported and are connected to a carriage shaft 75 through suitable support rods 76 having bearings 77 of Ithe needle ftyipe or any other suitable bearing construction. rIlhus, as the shaft 131 `is rotated, the idler gears are caused to rotate and impart a rotation to lthe carriage shaft 75. By reason of such planetary gear system G, the speed of the shaft is reduced vas com-pared to the speed of the shaft 131 and the motor shaft 25. In addition, fthe torque developed at the shaft 75 and therefore at the bit B is increased by reason of the gear train G as compared to .the torque developed at the motor shaft 25.

The shaft 75 is suitably connected with any coupling such as indicated at S0 to a shaft extension 81 which joins with lthe upper end of the shock absorber S. Thus, the 'shock absorber S is the same as that illustrated in FIGS. 3e5, but the shaft S1 replaces the shaft 31 of FIG. 4.

The pressure equalization apparatus E includes upper and lower heads S2 and 83 and a ilexible sleeve 84 formed of rubber `or other similar elastic material. A passage 82a in the head 82 communicates the area internally of the sleeve S4 with the area in the vicinity of fthe motor M and the clutch C, as well as the `gear train G. The area S5 externally of the sleeve 84 is in communication with the drilling rnud or other fluid which is circulating in the apparatus A-1 by fmelans of a mnd port 11C, the number of which may be varied as desired. The lower head 83 preferably carries la ilexible packing 83a which seals off the oil in the sleeve 84 from the mud below the head 83. Thus, with the eq-ulalizing apparatus E, r'the variations fin the mud and oil pressures may be compensated automatically while maintaining such mud and oil separately from each other.

'Phe operation of the apparatus of FIGS. 6 and 7 is .identical with that descr-ibed heretofore in connection with the lapparatus A of FIGS. 1-5, except for the function of the gear train G which provides the lower speed and increased torque at 4the bit B for a given motor speed at the motor M. The gear train G develops a considerable 7 amount of heat during rits operation and such heat is dissipated to the oil and then to the circula-ting mud which flows downwardly through the sleeve or cylinder 22 surrounding the housing 10, in the same manner as described heretofore in connection with FIG. l. The other portions of the apparatus A-`1 are likewise cooled by the circulating drilling mud or uid, which may be liquid or gas, during the drilling operation.

In FIG. 8, a further modification is illustrated wherein a turbine T is operated by drilling mud and is Used in place of the electric motor M. Thus, the turbine T is operated by the drilling mud or fluid which ows downwardly through the drill string and into the housing 10 for imparting rotation to the turbine T in a known manner. The turbine discharge flows into the housing or tubular body 10 below the turbine T in the vicinity of the turbine shaft 125 and is directed through inlet ports 111a to the sleeve or cylinder 22 for conducting the drilling mud or uid as in the previous rormsof the invention. It is to be noted that the shaft 125 is connected to a slip clutch C and that the apparatus below the slip clutch C is identical to that illustrated in FIG. 6. When the turbine T is used as the means for imparting rotation to` the drill bit B, Ithe clutch C and the shock absorber S serve primarily to protect the gear train G. In the absence of the slip clutch C and the shock absorber S, the gear train G could be severely damaged in the event the drill bit is intermittently subjected to extreme loads or is suddenly stopped, as explained heretofore in connection with the form of the invention shown in FIG. 1. Thus, the gear train life and dependability are appreciably enhanced by the inclusion of the clutch C and the shock absorber S in the driving connection from the turbine T to the drill bit B. The oil is employed below a bead or plate 116 having a lluidatight seal 116a around the shaft 125 (FIG. 8) so as to operate the turbine T within the drilling mud or uid while still separating such mud or fluid from the oil bath or chamber provided within the housing 10.

The foregoing disclosure and description of lthe invention is illustrative and explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

What is claimed is: 1. A well drilling apparatus, comprising: (a) a tubular body adapted to be supported in a well bore, (b) a drill bit mounted on the lower end of said body for rotation relative thereto, (c) a motor mounted in said tubular body, (d) drive means connecting said motor to said drill bit, (e) said drive means including,

(1) a slip clutch which is normally engaged for driving the drill bit with the motor but which is temporarily released for permitting rotation of the motor independently of the drill bit when the load on the bit exceeds a predetermined amount, and

(2) a shock absorber for transmitting rotational power from the motor to the bit and for absorbing intermittent shock loads imposed thereon, and

(f) means for circulating drilling iluid relative to said motor, slip clutch and shock absorber for removing heat generated, thereby during drilling operations with the drill bit.

2. A well drilling apparatus, comprising:

(a) a tubular body adapted to be supported in a well bore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) a motor mounted in said tubular body,

(d) drive means connecting said motor to said drill bit, (e) said drive means including,

(1) la slip clutch which is normally engaged for driving the drill bit with the motor but which is temporarily released for permitting rotation of the motor independently of the drill bit when the load on the bit exceeds a predetermined amount, and

(2) a shock absorber for transmitting rotational power from the motor to the bit and for absorbing intermittent shock loads imposed thereon,

(f) means within said body for sealing oit said motor and said slip clutch to provide a sealed area for an oil bath,

(g) an oil bath in said sealed area, and

(h) means for circulating drilling fluid around said oil bath to dissipate heat therefrom to thereby pre'- vent the motor and clutch from becoming overheated in use.

3. A well drilling apparatus, comprising:

(a) a tubular body adapted to be supported in a well bore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) a motor mounted in said tubular body,

(d) drive means connecting said motor to said drill bit,

(e) said drive means including,

(1) a slip clutch which is normally engaged for driving the drill bit with the motor but which is temporarily released for permitting rotation of the motor independently of the drill bit when the load on the bit exceeds a predetermined amount, and l (2) a shock absorber for transmitting rotational power from the motor to the bit and for absorbing intermittent shock loads imposed thereon, and

(f) means connecting said shock absorber to said slip clutch, whereby the shock absorber serves to intercept the intermittent shock loads from the bit and prevent same from being transmitted to said slip clutch to thereby avoid excessive wear on said slip clutch.

4. A well drilling apparatus, comprising:

(a) a tubular body adapted to be supported in a well bore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) ra power unit mounted in said tubular body,

(d) drive means connecting said power unit to said drill bit,

(e) said drive means including,

(1) .a slip clutch which is normally engaged for driving the drill bit with the power unit but which is temporarily released for permitting rotation of the power unit independently of the drill bit when the load on the bit exceeds a predetermined amount,

(2) a gear train connected to said slip clutch fo increasing the torque output from said power unit, and

(3) a shock absorber connected to said gear train and to said bit for intercepting and absorbing intermittent shock loads from said bit to prevent same from being transmitted to said gear'train.

5. A well drilling apparatus, comprising:

(a) a tubular body adapted to be supported in a well bore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) a motor mounted in said tubular body,

(d) an electrical cable in said tubular body andex- 9 tending from-the surface of therw'ell to said 'motor for v'supplying electrical power thereto, s

(e) drive v.means.connecting `said motor to "said drill bit, l

(f) said drive means including, i

(1) a slip clutch which is -nornally engaged for driving the drill bit with the :motor vbut 'Which is temporarily released for permitting rotation Aof the motor `independently of the drill bit when the load on the bit exceeds a predetermined amount,

(2) a shock absorber for transmitting rotational power from the motor to the bit and for absorbing intermittent shock loads imposed thereon,

(g) seal means for sealing off the tubular body from above said motor to below said slip clutch to provide an oil bath therein, and

(h) fluid passage means on said body for conducting drilling fluid from the tubular body externally of the area thereof sealed o by said seal means and then back to the tubular body for supplying the drill bit with such fluid.

6. A well drilling apparatus, comprising:

(a) a tubular body adapted to be supported in a well bore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) a power unit mounted in said tubular body,

(d) drive means connecting said power unit to said drill bit,

(e) said drive means including,

(1) a slip clutch which is normally engaged for driving the drill bit with the power unit but which is temporarily released for permitting rotation of the power unit independently of the drill bit when the load on the bit exceeds a predetermined amount,

(2) a gear train connected to said slip clutch for increasing the torque output from said power unit, and

(3) a shock absorber connected to said gear train and to said bit for intercepting and absorbing intermittent shock loads from said bit to prevent same from being transmitted to said gear train,

(f) an electrical cable in said tubular body and extending from the surface of the well to said motor for supplying electrical power thereto,

(g) seal means for Isealing 01T said tubular body from above said motor to below said gear train to provide an oil bath therein, and

(h) uid lpassage means for conducting drilling fluid from said tubular body externally of the area sealed ofi by said seal means and then back to said tubular body for removing heat generated by said shock absorber.

7. A well drilling apparatus, comprising:

(a) a motor adapted to be connected to a drill bit,

(b) a drill bit,

(c) drive means connecting said motor to said drill bit,

(d) said drive means including a slip clutch having an outer shell and an inner plug which are frictionally engaged Vfor transmitting normal torque loads but which move independently of each other when a predetermined torque orce acts on either the shell or the plug,

(e) said outer shell being open at one end for substantially radial exing, and

(f) expander means forming part of said plug means for expanding portions of said plug means sub- -stantially radially outwardly into rictional engagement with the inner surface of said outer shell to set the clutch for release at said predetermined torque acting thereon.

8. A well drilling apparatus, comprising:

Uli

vl() (a)J a tubular body adapted to be supported in a well ore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) a motor mounted in said tubular body,

(d) drive means connecting said'motor to said drill bit, Y

(e) said drive means including,

(1) a slip clutch which yis normally engaged for driving the drill bit with the motor but which is temporarily released for permitting rotation of the motor independently of the drill bit when the load on the bit exceeds a predetermined amount, and

(2) means for transmitting rotational power from the motor to the bit and for absorbing intermittent shock loads imposed thereon, and

(f) means for circulating drilling iluid relative to said motor, slip clutch and said last-named means for removing heat generated thereby during drilling operations with the drill bit.

9. A well drilling apparatus, comprising:

(a) a tubular body adapted to be supported in a well bore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) a motor mounted in said tubular body,

(d) drive means connecting said motor to said drill bit,

(e) said drive means including,

(1) a slip clutch which is normally engaged for driving the drill bit with the motor but which is temporarily released for permitting rotation of the motor independently of the drill bit when the load on the bit exceeds a predetermined amount, and

(2) means for transmitting rotational power from the motor to the bit and for absorbing intermittent shock loads imposed thereon, and

(f) means connecting the last-named means to said slip clutch whereby said last-named means serves to intercept the intermittent shock loads from the bit and prevent the full effect thereof from being transmitted to said slip clutch to thereby avoid excessive wear on said slip clutch.

10. A well drilling apparatus, comprising:

(a) a tubular body adapted to be supported in a well bore,

(b) a drill bit mounted on the lower end of said body for rotation relative thereto,

(c) a power unit mounted in said tubular body,

(d) drive means connecting said unit to said drill bit,

(e) said drive means including,

(l) a slip clutch which is normally engaged for driving the drill bit with the power unit but which is temporarily released for permitting rotation of the power unit independently of the drill bit when the load on the bit exceeds a prede termined amount,

(2) a gear train connected to said slip clutch for increasing the torque output from said power unit, and

(3) means connected to said gear train and to said bit for intercepting and absorbing intermittent shock loads from said bit to prevent the full effect thereof from being transmitted to said gear train.

References Cited by the Examiner UNITED STATES PATENTS 309,679 12/ 1884 Bacon 64-27 859,976 7/ 1907 Procunier 64-30 1,087,089 2/1914 Trotter 173--146 X (Other references on following page) UNITED Schmid 64-30 Thornburg 173--163 X Degen 175-92 X Billups 64-30 FOREIGN PATENTS Germany.

CHARLES E. OCONNELL, Primary Examiner. 

7. A WELL DRILLING APPARATUS, COMPRISING: (A) A MOTOR ADAPTED TO BE CONNECTED TO A DRILL BIT, (B) A DRILL BIT, (C) DRIVE MEANS CONNECTING SAID MOTOR TO SAID DRILL BIT, (D) SAID DRIVE MEANS INCLUDING A SLIP CLUTCH HAVING AN OUTER SHELL AND AN INNER PLUG WHICH ARE FRICTIONALLY ENGAGED FOR TRANSMITTING NORMAL TORQUE LOADS BUT WHICH MOVE INDEPENDENTLY OF EACH OTHER WHEN A PREDETERMINED TORQUE FORCE ACTS ON EITHER THE SHELL OR THE PLUG, (E) SAID OUTER SHELL BEING OPEN AT ONE END FOR SUBSTANTIALLY RADIAL FLEXING, AND (F) EXPANDER MEANS FORMING PART OF SAID PLUG MEANS FOR EXPANDING PORTIONS OF SAID PLUG MEANS SUBSTANTIALLY RADIALLY OUTWARDLY INTO FRICTIONAL ENGAGEMENT WITH THE INNER SURFACE OF SAID OUTER SHELL TO SET THE CLUTCH FOR RELEASE AT SAID PREDETERMINED TORQUE ACTING THEREON. 